"Crafty" is this Michigander's middle nameGive Wayne Guntzviller a code and he’ll crack it—a QR code, that is. Together with his wife and business partner, Beth, ­Guntzviller has turned his store, Miner’s North Jewelers—located in Traverse City, Mich., where the population balloons from 15,000 to nearly 2 million every summer when out-of-towners descend for tourist season—into a retail referendum on the mobile marketing power of Quick Response codes. Readable by smartphones, the two-dimensional barcodes are plastered all over the store, thereby enabling Guntzviller to virtually greet, acknowledge, and educate hundreds of customers with a simple scan of their phones.Why are you making your store a QR code superstore and what will that entail? Our store is located in a vibrant downtown business district that has two busy selling seasons. Whether it’s the summer tourist season